A (collar-equipped) piston and a piston-equipped assembly for a hydraulic unit or a piston-cylinder device of a vehicle braking system, includes a contact surface for a sealing collar, which has a shape curving away from the sealing collar, formed on the piston, so that the sealing collar is pressable, at least partially, into a displacement volume, which is spanned by the contact surface of the piston, with a pressure which is present on a side of the sealing collar directed away from the piston. Also described is a hydraulic unit and a piston-cylinder device for a vehicle braking system, and a vehicle braking system. Further described is a manufacturing method for a piston for a hydraulic unit or a piston-cylinder device of the braking system, and a manufacturing method for a piston-equipped assembly for a hydraulic unit or a piston-cylinder device of the braking system.